Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests

<div>Effects of the unloading conditions on the fractal dimension of surface cracks. (a) Fractal dimension with different initial unloading confining pressures. (b) Fractal dimension with different unloading rates.</div>

Advances in Materials Science and Engineering

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Figure 7

Figure 7: Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests 